1. Technical Field
The present invention relates to an optical receiver, a spatial optical transmission method, a spatial optical transmitter, and an optical transmission method, which use light as a medium.
2. Background Art
Recently, wireless devices have been increased, and there among optical transmitters using light as a transmission medium of data have been increased.
As shown as an IrDA receiver in Denshi-Gijutu Dec. p. 30 (1996), a receiver of a conventional optical transmitter is composed of a photodiode, an amplifier, and a comparator, and an optical signal is converted into an electric signal by the photodiode and is amplified by the amplifier to be quantized by the comparator.
This type of structure has such a defect that an error arises or a jitter arises because quantization is failed in the capacitor due to a dull waveform instead of rectangular pulses to be obtained if response speed of an LED and the photodiode that are used in the transmitter is not sufficient to a signal transmitted.
Then, normally, the LED and photodiode that are sufficiently high-speed to the signal transmitted are used. Nevertheless, in case large volume of data such as images is transmitted at high-speed, there is such a task that it becomes necessary to have a transmission band that is faster than or equal to the response speed of the LED and photodiode.
In addition, if it is attempted to perform plural system of data transmission on the same optical path in the conventional structure, jamming arises due to optical interference. For this reason, there is another task that it is impossible to extend the transmission band with the method of multiplexing the plural system of data on the same optical path.
An object of the present invention, in consideration of such conventional tasks, is to provide an optical receiver, a spatial optical transmission method, a spatial optical transmitter, and an optical transmission method, which can widen a transmission band width of a data communication using light as an medium.
The first invention of the present invention is an optical receiver comprising a photoelectric conversion means receiving an optical signal and converting the optical signal into an electric signal, a signal edge detecting means detecting edge information from said converted electric signal, a quantizing means generating signal quantized on the basis of said detected edge signal, an amplification factor changing means amplifying an output signal from said photoelectric conversion means with a predetermined amplification factor, and a signal level detecting means detecting a signal level of an output of said signal edge detecting means and controlling said amplification factor on the basis of the detection result, wherein the output signal of said amplification factor changing means is inputted to said quantizing means.
Owing to this, for example, it becomes possible to reduce the effect of degradation of a signal caused by a light-emitting device and a light-receiving device and to widen the transmission bandwidth.
A further aspect of the present invention is a spatial optical transmission method that is a spatial optical transmission method for transmitting data through spatially emitting light, wherein said method is for transmitting two lines of data transmission on the substantially same optical path with using linearly-polarized light whose polarized directions are orthogonal to each other.
Another aspect of the present invention is a spatial optical transmission method that is a spatial optical transmission method for transmitting data through spatially emitting light, wherein said method is for transmitting two lines of data transmission on the substantially same optical path with using circularly-polarized light respective rotational directions of polarization of which are reverse. polarized-beam-splitting means.
A still further aspect of the present invention is an optical transmission method that is an optical transmission method for transmitting data with using light, wherein said method is for simultaneously transmitting different lines of data on the practically same optical path with using linearly-polarized light the polarized directions of which are orthogonal to each other or circularly-polarized light the rotational directions of which are reverse to each other.
Owing to this, it becomes possible to multiplex two systems of data transmission on the practically same optical path and to widen the transmission bandwidth.